Encoder apparatus using liquid to suppress detection failure

ABSTRACT

An encoder apparatus comprises a first scale member with a scale region on which a scale is arranged; a detector that detects light from the scale region; and a retaining member with a retaining surface that is arranged so as to face a surface of the first scale member including the scale region via a predetermined gap, and that retains a liquid at least between the retaining surface and the first scale member.

This is a Continuation application of International Patent ApplicationNo. PCT/JP2009/058414, filed on Apr. 28, 2009, which claims priority toJapanese Patent Application No. 2008-118443, filed on Apr. 30, 2008, andclaims priority to and the benefit of U.S. Provisional Application No.61/202,669, filed on Mar. 25, 2009. The contents of the aforementionedapplications are incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to an encoder apparatus.

BACKGROUND

As a position detection apparatus, encoder apparatuses as disclosed in,for example, the following patent documents are known.

-   Patent Document 1: Japanese Unexamined Patent Application, First    Publication No. H05-133768-   Patent Document 2: Japanese Unexamined Patent Application, First    Publication No. H05-118873

Encoder apparatuses use a detector to detect a scale member on which ascale is arranged. If a surface state of the scale member isdeteriorated by, for example, foreign matter being attached to thesurface of the scale member, there is a possibility that a detectionfailure will occur.

Aspects of the present invention have an object to provide an encoderapparatus capable of suppressing an occurrence of a detection failure.

SUMMARY

According to a first aspect of the present invention, there is providedan encoder apparatus including: a first scale member with a scale regionincluding a scale; a detector that detects light from the scale region;a retaining member with a retaining surface that faces the scale regionvia a gap and retains a liquid at least between the retaining surfaceand the first scale member.

According to a second aspect of the present invention, there is providedan encoder apparatus including: a first scale member with a scale regionincluding a scale; a detector that detects the scale of the scaleregion; and a liquid supply port that supplies a liquid so as to be incontact with a region on the first scale member including the scaleregion.

According to the aspects of the present invention, it is possible tosuppress occurrence of a detection failure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view showing a part of an encoder apparatusaccording to a first embodiment.

FIG. 2 is a side cross-sectional view showing the encoder apparatusaccording to the first embodiment.

FIG. 3 is a plan view showing a moving scale according to the firstembodiment.

FIG. 4 is an enlarged side cross-sectional view showing a part of amoving scale and a retaining member according to the first embodiment.

FIG. 5 is an enlarged side cross-sectional view showing a part of amoving scale and a retaining member according to the first embodiment.

FIG. 6 is an enlarged side cross-sectional view showing a part of amoving scale and a retaining member according to the first embodiment.

FIG. 7A is a perspective view showing a part of an encoder apparatusaccording to a second embodiment.

FIG. 7B is a cross-sectional view of FIG. 7A taken through A-A asindicated by arrowheads.

FIG. 7C is a cross-sectional view of FIG. 7A taken through B-B asindicated by arrowheads.

FIG. 8 is a side cross-sectional view showing an encoder apparatusaccording to a third embodiment.

FIG. 9 is a side cross-sectional view showing an encoder apparatusaccording to a fourth embodiment.

FIG. 10 is a perspective view showing a part of an encoder apparatusaccording to a fifth embodiment.

FIG. 11 is a side cross-sectional view showing an encoder apparatusaccording to a sixth embodiment.

FIG. 12 is a perspective view of a retaining member according to thesixth embodiment, seen from below.

FIG. 13 is a side cross-sectional view showing an encoder apparatusaccording to the sixth embodiment.

FIG. 14 is a side cross-sectional view showing an encoder apparatusaccording to a seventh embodiment.

FIG. 15 is a side cross-sectional view showing an encoder apparatusaccording to an eighth embodiment.

FIG. 16 is a side cross-sectional view showing an encoder apparatusaccording to a ninth embodiment.

DESCRIPTION OF EMBODIMENTS

Hereunder is a description of embodiments of the present invention withreference to the drawings. However, the present invention is not limitedto these. In the following description, an XYZ orthogonal coordinatesystem is established, and the positional relationship of respectivemembers is described with reference to this XYZ orthogonal coordinatesystem. A predetermined direction within a horizontal plane is made theX axis direction, a direction orthogonal to the X axis direction in thehorizontal plane is made the Y axis direction, and a directionorthogonal to both the X axis direction and the Y axis direction (thatis, a vertical direction) is made the Z axis direction. Furthermore,rotation (inclination) directions around the X axis, the Y axis, and theZ axis are made the θX, the θY, and the θZ directions, respectively.

First Embodiment

A first embodiment will be described. FIG. 1 is a perspective viewshowing a part of an encoder apparatus 1 according to the firstembodiment. FIG. 2 is a side cross-sectional view of the encoderapparatus 1 according to the first embodiment.

In FIG. 1 and FIG. 2, the encoder apparatus 1 includes: a first scalemember 4 with a scale region (a detection region) 3 on which a scale 2is arranged; a detector 5 that detects light from the scale region 3;and a retaining member 7 with a retaining surface 6 that is arranged soas to face a surface of the first scale member 4 via a predetermined gapand retains a liquid LQ between itself and the first scale member 4.Furthermore, the encoder apparatus 1 includes: a light source 8 thatemits light; and an optical system 9 is which the light from the lightsource 8 is incident. In FIG. 1, the illustration of the detector 5, thelight source 8, and the optical system 9 is omitted. In the presentembodiment, water is used as the liquid LQ.

The encoder apparatus 1 of the present embodiment is a rotary encoder.The first scale member 4 is a circular plate that rotates. The firstscale member 4 is coupled to a rod 10. The first scale member 4 rotateswith the rod 10 as its axis of rotation. In the present embodiment, theaxis of rotation of the first scale member 4 is substantially parallelto the Z axis.

The first scale member 4 moves with respect to the detector 5. Theposition of the retaining member 7 is fixed with respect to the detector5. In the present embodiment, the retaining member 7 includes: a secondscale member 11 that is different from the fast scale member 4; atransmissive member 12 that allows light to be transmitted through; anda support member 13 that supports the second scale member 11 and thetransmissive member 12. In the following description, the first scalemember 4 is appropriately referred to as the moving scale 4, and secondscale member 11 is appropriately referred to as the fixed scale 11.

The moving scale 4 has: a transmissive member capable of transmittinglight; and a scale (a scale pattern) 2 that is formed from alight-shielding material on the transmissive member. The fixed scale 11has: a transmissive member capable of transmitting light; and a scale (ascale pattern) that is formed from a light-shielding material on thetransmissive member. The transmissive members of the moving scale 4 andthe fixed scale 11 are made of, for example, silica. The light-shieldingmembers thereof are made of, for example, chromium. The support member13 is made of a metal such as titanium.

The moving scale 4 is a plate member that has: a top surface 4A; abottom surface 4B that faces in a direction opposite to a top surface4A; and a side surface 4S that connects the top surface 4A with thebottom surface 4B. The top surface 4A and the bottom surface 4B of themoving scale 4 are substantially parallel to each other. That is, themoving scale 4 is a parallel flat plate. In the present embodiment, thetop surface 4A and the bottom surface 4B are substantially parallel tothe XY plane. In the present embodiment, the scale region 3 is arrangedon a part of the top surface 4A of the moving scale 4. In the presentembodiment, the scale region 3 is a ring-shaped region on a part of thetop surface 4A.

The retaining member 7 is a ring-shaped member. The retaining member 7has a first portion 71 that faces at least a part of the top surface 4A;a second portion 72 that faces at least a part of the bottom surface 4B;and a third portion 73 that connects the first portion 71 with thesecond portion 72 and faces the side surface 4S. The first portion 71 isarranged so as to face at least the scale region 3.

In the present embodiment, the first portion 71 is composed of the fixedscale 11 and a part of the support member 13. The second portion 72 iscomposed of the transmissive member 12 and a part of the support member13. The third portion 73 is composed of a part of the support member 13.

In the present embodiment, the retaining member 7 retains the liquid LQbetween itself and the moving scale 4 so that a local region on thesurface of the moving scale 4 is in contact with the liquid LQ. Theretaining member 7 retains the liquid LQ between itself and the movingscale 4 so that at least the scale region 3 is in contact with theliquid LQ.

In the present embodiment, the first portion 71 is formed in a ringshape so as to face the ring-shaped region on a part of the top surface4A including the scale region 3. The second portion 72 is formed in aring shape so as to face the ring-shaped region on a part of the bottomsurface 4B. The third portion 73 is formed in a ring shape so as tosurround the side surface 4S.

The retaining surface 6 includes: a bottom surface of the first portion71 that faces the top surface 4A; a top surface of the second portion 72that faces the bottom surface 4B; and a side surface of the thirdportion 73 that faces the side surface 4S. In this manner, in thepresent embodiment, the retaining surface 6 is formed in a ring shape inaccordance with the moving scale 4.

The fixed scale 11 is a plate member that has: a top surface 11A; and abottom surface 11B that faces in the direction opposite to the topsurface 11A. A scale of the fixed scale 11 is arranged on the bottomsurface 11B. The top surface 11A and the bottom. surface 11B of thefixed scale 11 are substantially parallel to each other. That is, thefixed scale 11 is a parallel flat plate. In the present embodiment, thetop surface 11A and the bottom surface 11B are substantially parallel tothe XY plane. The bottom surface 11B of the fixed scale 11 faces the topsurface 4A of the moving scale 4. The fixed scale 11 is capable ofretaining the liquid LQ between the bottom surface 11B and the movingscale 4. That is, in the present embodiment, the retaining surface 6includes the bottom surface 11B.

The transmissive member 12 is a plate member that has a top surface 12A,and a bottom surface 12B that faces in the direction opposite to the topsurface 12A. The top surface 12A and the bottom surface 12B of thetransmissive member 12 are substantially parallel to each other. Thatis, the transmissive member 12 is a parallel flat plate. In the presentembodiment, the top surface 12A and the bottom surface 12B aresubstantially parallel to the XY plane. The top surface 12A of thetransmissive member 12 faces the bottom surface 4B of the moving scale4. The transmissive member 12 is capable of retaining the liquid LQbetween the top surface 12A and the moving scale 4. That is, in thepresent embodiment, the retaining surface 6 includes the top surface12A.

In the present embodiment, the scale 2 of the moving scale 4 is alight-dark grating pattern (hereinafter referred to as the grating)formed on the top surface 4A. The grating of the moving scale 4 is aone-dimensional grating whose periodic direction is along a rotationdirection of the moving scale 4 (the θZ direction). In the presentembodiment, the moving scale 4 is of transmissive type.

The fixed scale 11 is arranged above the moving scale 4 (on the +Zside). The fixed scale 11 is arranged at a position that faces the scaleregion 3 of the top surface 4A. The scale of the fixed scale 11 is alight-dark grating pattern (hereinafter referred to as the grating)formed on the bottom surface 11B. The grating of the fixed scale 11 is aone-dimensional grating whose periodic direction is along the θZdirection. In the present embodiment, the fixed scale 11 is oftransmissive type.

The optical system 9 is arranged at a position facing the to surface 11Aof the fixed scale 11. The optical system 9 is arranged between thelight source 8 and the fixed scale 11, and collimates light emitted fromthe light source 8. The fixed scale 11 is arranged between the opticalsystem 9 and the moving scale 4. The light source 8 is, for example, anLED, and emits coherent light. The light emitted from the light source 8is converted into parallel light by the optical system 9, which areincident on the fixed scale 11. The light incident on the fixed scale 11is transmitted through (pass through) the fixed scale 11 and areirradiated onto the scale region 3 of the moving scale 4.

As shown in FIG. 2, in the present embodiment, the light source 8 andthe optical system 9 are arranged in a space 15 formed by a housing 14.The housing 14 forms the space 15 between itself and the retainingmember 7 (the first portion 71).

The transmissive member 12 is arranged below the moving scale 4 (on the−Z side). The transmissive member 12 is arranged at a position thatfaces the bottom surface 4B. The detector 5 is arranged at a positionthat faces the bottom surface 12B of the transmissive member 12. Thetransmissive member 12 is arranged between the moving scale 4 and thedetector 5.

FIG. 3 is a plan view showing the moving scale 4. As shown in FIG. 3,the scale region 3 is a ring-shaped region on a part of the top surface4A. The scale region 3 is lyophilic to the liquid LQ (has lyophilicproperty). The contact angle of the scale region 3 with respect to theliquid LQ is, for example, less than 90 degrees.

In the present embodiment, a lyophilic treatment is carried out to themoving scale 4, to thereby provide (impart) lyophilic property(lyophilicity) to the scale region 3. The lyophilic treatment includes,for example, a silane coupling treatment. In the present embodiment, asilane coupling treatment is carried out to the moving scale 4 on whichthe scale 2 is formed, to thereby form OH groups on a partial region(the scale region 3) of the surface (the top surface 4A) of the movingscale 4. Thus, lyophilic property is provided to the scale region 3.

In the present embodiment, with respect to the radiation directionaround the rotation center of the moving scale 4, a first region 16 withlyophobic property to the liquid LQ is arranged external side of thescale region 3, and a second region 17 with lyophobic property to theliquid LQ is arranged inner side of the scale region 3. The first andsecond regions 16, 17 are ring-shaped regions arranged on a part of thetop surface 4A. The contact angle of the first and second regions 16, 17with respect to the liquid LQ is, for example, not less than 90 degrees.Thus, in the present embodiment, the surrounding areas of the scaleregion 3 have lyophobic property (lyophobic) to the liquid LQ.

In the present embodiment, a lyophobic treatment is carried out to themoving scale 4, to thereby provide lyophobic property to the first andsecond regions 16, 17. The lyophobic treatment includes, for example, atreatment of forming lyophobic films on the moving scale 4. Thelyophobic film includes, for example, an amorphous fluorine resin(hydrofluoroether). In the present embodiment, the lyophobic film isformed of “Cytop” manufactured by Asahi Glass Co., Ltd. The lyophobicfilms can be formed on the moving scale 4 by a predetermined coatingmethod such as spin coating. Note that the lyophobic films can be formedon the moving scale 4 by a wet process such as dipping. In the presentembodiment, the lyophobic property is provided to the first and secondregions 16, 17 by forming the lyophobic films including fluorine onpartial regions (the first and second regions 16, 17) of the surface(the top surface 4A) of the moving scale 4 on which the scale 2 isformed.

In the example shown in FIG. 3, with respect to the radiation directionaround the rotation center of the moving scale 4, a partial externalside of the scale 2 and a partial inner side of the scale 2 are arrangedin the first and second regions (lyophobic regions) 16, 17.

FIG. 4 is an enlarged side cross-sectional view of a part of the movingscale 4 and the retaining member 7. As shown in FIG. 4, the retainingsurface 6 of the retaining member 7 includes a first surface 18 thatfaces the moving scale 4 via a first gap G1, and a second surface 19that faces the moving scale 4 via a second gap G2 which is smaller thanthe first gap G1. In the present embodiment, the first surface 18 andthe second surface 19 are arranged on both the first portion 71 and thesecond portion 72 respectively. The fast surface 18 of the fast portion71 faces the top surface 4A via the first gap G1. The second surface 19of the first portion 71 faces the top surface 4A via the second gap G2.The first surface 18 of the second portion 72 faces the bottom surface4B via the first gap G1. The second surface 19 of the second portion 72faces the bottom surface 4B via the second gap G2.

In the present embodiment, at least a part of the second surface 19 ofthe first portion 71 faces an external region of the scale region 3. Inthe present embodiment, at least a part of the second surface 19 facesthe second region 17 that is lyophobic to the liquid LQ. In addition, inthe present embodiment, a partial region of the bottom surface 4B thatfaces the second surface 19 of the second portion 72 is also lyophobicto the liquid LQ.

Furthermore, in the present embodiment, the second surfaces 19 arelyophilic to the liquid LQ. The contact angle of the second surface 19with, respect to the liquid LQ is less than 90 degrees. A lyophilictreatment such as a silane coupling treatment is carried out to thesecond surfaces 19, to thereby provide lyophilic property to the secondsurfaces 19.

At least a part of the first surface 18 faces the scale region 3. Thefirst surfaces 18 are lyophilic to the liquid LQ. The contact angle ofthe first surface 18 with respect to the liquid LQ is less than 90degrees. A lyophilic treatment such as a silane coupling treatment iscarried out to the fast surfaces 18, to thereby provide lyophilicproperty to the first surfaces 18. In the present embodiment, the firstsurface 18 includes the bottom surface 11B of the fixed scale 11 and thetop surface 12A of the transmissive member 12.

In the present embodiment, the second surfaces 19 are substantiallyparallel to the XY plane. Within the XY plane, the second surface 19 hasa ring shape. The second surfaces 19 are arranged at innercircumferential edges of the retaining surface 6 so as to face themoving scale 4.

Next is a description of an example of an operation of the encoderapparatus 1 with the aforementioned construction.

Between the retaining member 7 and the moving scale 4, the liquid LQ isretained. The liquid LQ is retained between the retaining member 7 andthe moving scale 4 so as to be in contact with a partial region of thetop surface 4A, a partial region of the bottom surface 4B, and the sidesurface 4S of the moving scale 4 including the scale region 3.Furthermore, the liquid LQ is retained between the retaining member 7and the moving scale 4 so as to be in contacted with the retainingsurface 6 of the retaining member 7 including the bottom surface 11B ofthe fixed scale 11 and the top surface 12A of the transmissive member12. With the liquid LQ retained between the moving scale 4 and theretaining member 7, an internal space 20 formed between the moving scale4 and the retaining member 7 is filled with the liquid LQ.

In a state with the internal space 20 being filled with the liquid LQ,light is emitted from the light source 8. The light emitted from thelight source 8 is incident on the fixed scale 11 via the optical system9. The light being transmitted through the fixed scale 11 is incident onthe scale region 3 of the moving scale 4 via the liquid LQ. The lightincident on the scale region 3 of the moving scale 4 is transmittedthrough the moving scale 4, and is then incident on the transmissivemember 12 via the liquid LQ. The light incident on the transmissivemember 12 is transmitted through the transmissive member 12, and is thenincident on the detector 5. The detector 5 detects the light from thescale region 3 of the moving scale 4 via the transmissive member 12 andthe liquid LQ. In this manner, in the present embodiment, the detector 5detects the light, which has transmitted through the moving scale 4, viathe liquid LQ.

In the present embodiment, the light from the light source 8 isirradiated onto the fixed scale 11 via the optical system 9. The lightbeing transmitted through the fixed scale 11 has a light-dark pattern.As is well known, if the scale pitch is fine, diffraction occurs.However, the scale pitch (for example, 0.2 mm) in the present embodimentis sufficiently large for the wavelength of light (for example, 850 nm).This makes diffraction substantially negligible.

The light being transmitted through the fixed scale 11 is incident onthe moving scale 4 with a pitch identical to that of the fixed scale 11,allowing only the light (the amount of light) that has transmittedthrough the moving scale 4 to be incident on the detector 5.

In the encoder apparatus 1 with the aforementioned construction, themovement (rotation) of the moving scale 4 changes the positionalrelationship between the fixed scale 11 and the moving scale 4.Accordingly, the amount of light detected by the detector 5 changesperiodically. With the detection of the change in the amount of light,the position information on the moving scale 4 in its rotationaldirection can be measured.

In the present embodiment, the liquid LQ is retained between the movingscale 4 and the retaining member 7. This suppresses attachment offoreign matter to the surface of the moving scale 4. In the presentembodiment, the liquid LQ is retained between the moving scale 4 and theretaining member 7, and the internal space 20 formed between the movingscale 4 and the retaining member 7 is filled with the liquid LQ. Theliquid LQ in the internal space 20 is always kept in contact with thesurface of the moving scale 4 (that includes a part of the top surface4A including the scale region 3; a part of the bottom surface 4B; andthe side surface 4S). This suppresses attachment of foreign matter tothe surface of the moving scale 4.

In the present embodiment, the moving scale 4 and the retaining member 7face each other via the gaps. That is, the moving scale 4 is spaced(separated) from the retaining member 7. This makes the moving scale 4smoothly movable (rotatable) with respect to the retaining member 7. Inthe present embodiment, openings 21 are formed between the moving scale4 and the retaining member 7. The openings 21 are filled with (occupiedby) the liquid LQ. This suppresses intrusion of foreign matter from anexternal space into the internal space 20 via the openings 21. Even ifforeign matter has intruded into the internal space 20, attachment ofthe foreign matter to the surface of the moving scale 4 is suppressed bythe liquid LQ in the internal space 20.

As described above, according to the present embodiment, the retainingmember 7 with the retaining surface 6 that retains the liquid LQ betweenitself and the moving scale 4 is established. Therefore, it is possibleto suppress attachment of foreign matter to the surface of the movingscale 4. In the present embodiment, the liquid LQ is retained so as tobe contact with at least the scale region 3 of the surface of the movingscale 4. Therefore, it is possible to suppress attachment of foreignmatter to the scale region 3. Furthermore, according to the presentembodiment, the liquid LQ is kept in contact also with the bottomsurface 11B of the fixed scale 11 and the top surface 12A of thetransmissive member 12. This suppresses attachment of foreign matter tothe bottom surface 11B and the top surface 12A. Therefore, it ispossible to suppress occurrence of a detection failure.

According to the present embodiment, the retaining member 7 retains theliquid LQ between itself and the moving scale 4 so that the liquid LQ isin contact with a local region on the surface of the moving scale 4including the scale region 3. This allows for smooth movement (rotation)of the moving scale 4. For example, the viscous resistance of the liquidLQ that acts on the moving scale 4 can be made lower, and hence, themoving scale 4 can be moved (rotated) more smoothly when the movingscale 4 is moved (rotated) in a state with a partial region (a localregion) on the surface of the moving scale 4 being in contact with theliquid LQ than when the moving scale 4 is moved (rotated) in a statewith the whole region on the surface of the moving scale 4 being incontact with the liquid LQ.

According to the present embodiment, the retaining surface 6 has a ringshape in accordance with the shape of the scale region 3. Therefore, thescale region 3 is allowed to be always kept in contact with the liquidLQ. This suppresses attachment of foreign matter to the scale region 3.

According to the present embodiment, the scale region 3 is lyophilic tothe liquid LQ. Hence, the scale region 3 is capable of being in closecontact with the liquid LQ. Accordingly, attachment of for example,bubbles or the like to the scale region 3 can be suppressed. Therefore,it is possible to suppress occurrence of a detection failure.

According to the present embodiment, the first and second regions 16, 17external side of the scale region 3 are lyophobic to the liquid LQ. Thiscan suppresses flowing out of the liquid LQ that is retained between themoving scale 4 and the retaining member 7 into the external space.Furthermore, in the present embodiment, between the second surface 19arranged at an inner circumferential edge of the retaining surface 6 andthe second region 17 that is lyophobic to the liquid LQ, an interface (ameniscus) of the liquid LQ in the internal space 20 is formed. Thissuppresses flowing out of the liquid LQ in the internal space 20 intothe external space.

In the present embodiment, the retaining surface 6 includes the firstsurface 18 that faces the top surface 4A (the bottom surface 4B) of themoving scale 4 via the first gap G1; and the second surface 19 thatfaces the top surface 4A (the bottom surface 4B) via the second gap G2.With the second gap G2 set to a predetermined size (for example,approximately 0.1 to 2 mm), flowing out of the liquid LQ in the internalspace 20 into the external space is suppressed by the surface tension ofthe liquid LQ. Furthermore, because the first surfaces 18 are spaced(separated) from the moving scale 4, it is possible to enlarge theinternal space 20 filled with the liquid LQ.

In the aforementioned first embodiment, the description has been for thecase where the surface of the moving scale 4 that faces the secondsurfaces 19 is lyophobic to the liquid LQ, by way of example. However,the surface of the moving scale 4 may be has lyophilic property.

Note that, as shown in FIG. 5, on each of the top surface 4A and thebottom surface 4B of the moving scale 4, a protrusion portion 22 thatprotrudes toward the retaining surface 6 may be provided. The protrusionportions 22 are arranged at a position that faces the second surfaces 19along (of) the circumferential edges of the retaining surface 6. In theexample shown in FIG. 5, the top surface of the protrusion portion 22that faces the second surface 19 of the first portion 71 is a flatsurface, and is substantially parallel to the second surface 19.Similarly, the bottom surface of the protrusion portion 22 that facesthe second surface 19 of the second portion 72 is a flat surface, and issubstantially parallel to the second surface 19. With the moving scale 4provided with the protrusion portions 22 protruding toward the retainingsurface 6 at a position that faces the second surfaces 19 of thecircumferential edges of the retaining surface 6, it is possible tosuppress flowing out of the liquid LQ in the internal space 20 into theexternal space.

Note that, as shown in FIG. 6, the top surface (the bottom surface) ofthe protrusion portion 22B that faces the retaining surface 6 may beinclined (sloped) so as to be gradually closer to the retaining surface6 in the direction from the center of the retaining surface 6 to theexternal side thereof, in other words, in the direction from theinternal space 20 to the external space (the openings 21). Furthermore,the second surfaces 19 along the inner circumferential edges of theretaining surface 6 may be inclined so as to be gradually closer to themoving scale 4 in the direction from the center of the retaining surface6 to the external side thereof (in the direction from the internal space20 to the external space). In the example shown in FIG. 6, the firstsurfaces 18 are substantially parallel to the scale region 3. Each,second surface 19 is inclined with respect to each first surface 18.Also with this construction, it is possible to suppress flowing out ofthe liquid LQ in the internal space 20 into the external space.

Second Embodiment

Next is a description of a second embodiment. In the followingdescription, components the same as or similar to those of theaforementioned embodiment are denoted by the same reference symbols, anddescriptions thereof are simplified or omitted.

FIG. 7A is a perspective view showing a part of an encoder apparatus 1Baccording to the second embodiment. FIG. 7B is a cross-sectional view ofFIG. 7A taken through A-A as indicated by arrowheads. FIG. 7C is across-sectional view of FIG. 7A taken through B-B as indicated byarrowheads.

As shown in FIG. 7A through FIG. 7C, the encoder apparatus 1B accordingto the present embodiment includes a retaining member 7B that retains aliquid LQ between itself and a moving scale 4. Within the XY plane, theretaining member 7B is an arcuate member (circular arc member). Theretaining member 7B has a retaining surface 6B that retains the liquidLQ between itself and the moving scale 4. The retaining surface 6Bincludes first surfaces 18B that face the moving scale 4 each via afirst gap G1, and second surfaces 19B that face the moving scale 4 eachvia a second gap G2. Within the XY plane, each second surface 19B isarranged on a part around each first surface 18B. In the presentembodiment, the retaining member 7B retains the liquid LQ between itselfand a part of the scale region 3 in the θZ direction.

According to the present embodiment, the amount of the liquid LQretained between the retaining member 7B and the moving scale 4 issmall. Therefore, it is possible to make the viscous resistance of theliquid LQ that acts on the moving scale 4 low. Hence, it is possible tosmoothly move (rotate) the moving scale 4.

Third Embodiment

Next is a description of a third embodiment. In the followingdescription, components the same as or similar to those of theaforementioned embodiment are denoted by the same reference symbols, anddescriptions thereof are simplified or omitted.

FIG. 8 is a side cross-sectional view showing one example of an encoderapparatus 1C according to the third embodiment. In the presentembodiment, the encoder apparatus 1C has a reflective-type moving scale4C. A scale 2 (a scale region 3) is arranged on a top surface 4A of amoving scale 4C.

In the present embodiment, a retaining member 7C faces the top surface4A of the moving scale 4C. The retaining member 7C includes a fixedscale 11C, and a support member 13C that supports the fixed scale 11C.The retaining member 7C has a retaining surface 6C that retains a liquidLQ between itself and the top surface 4A of the moving scale 4C. Theretaining surface 6C includes a first surface 18C, and second surfaces19C that are closer to the top surface 4A than the first surface 18C.Within the XY plane, the retaining surface 6C has a ring shape. In thepresent embodiment, the second surfaces 19C are arranged in a ring shapeeach on the inner side and the external side of the first surface 18Cwith respect to the radiation direction around the center of theretaining member 7C.

A light source 8 is arranged at a position that faces the top surface11A of the fixed scale 11C. In the present embodiment, a detector 5 isarranged also at a position that faces the top surface 11A of the fixedscale 11C. The fixed scale 11C is arranged between the detector 5 andthe moving scale 4C.

Next is a description of an example of an operation of the encoderapparatus 1C with the aforementioned construction. Light is emitted fromthe light source 8 in a state with the liquid LQ being retained betweenthe retaining surface 6C of the retaining member 7C and the top surface4A of the moving scale 4C. The light emitted from the light source 8 isincident on the scale region 3 of the moving scale 4C via the fixedscale 11C and the liquid LQ. The light incident on the scale region 3 ofthe moving scale 4C is reflected off the moving scale 4C, and is thenincident on the detector 5 via the liquid LQ and the fixed scale 11C.The detector 5 detects the light from the scale region 3 of the movingscale 4C via the fixed scale 11C and the liquid LQ. In this manner, inthe present embodiment, the detector 5 detects the light, which has beenreflected off the moving scale 4C, via the liquid LQ.

Also in the present embodiment, it is possible to suppress attachment offoreign matter to the scale region 3, and to thereby suppress occurrenceof a detection failure.

Fourth Embodiment

Next is a description of a fourth embodiment. In the followingdescription, components the same as or similar, to those of theaforementioned embodiment are denoted by the same reference symbols, anddescriptions thereof are simplified or omitted.

FIG. 9 is a side cross-sectional view of one example of an encoderapparatus 1D according to the fourth embodiment. The encoder apparatus1D includes a reflective-type moving scale 4D. As shown in FIG. 9, ascale region 3 is arranged on a side surface 4S of the moving scale 4D.A retaining member 7D includes a fixed scale 11D arranged at a positionthat faces the side surface 4S of the moving scale 4D, and a supportmember 13D that supports the fixed scale 11D. The retaining member 7Dretains a liquid LQ between itself and the side surface 4S of the movingscale 4D. The retaining member 7D has a ring shape, and is arranged soas to surround the moving scale 4D. A light source 8 and a detector 5are arranged at positions that face the fixed scale 11D. Light emittedfrom the light source 8 is incident on the scale region 3 on the sidesurface 4S of the moving scale 4D via the fixed scale 11D and the liquidLQ. The light incident on the scale region 3 of the moving scale 4D isreflected off the moving scale 4D, and is then incident on the detector5 via the liquid LQ and the fixed scale 11D. The detector 5 detects thelight from the scale region 3 of the moving scale 40 via the fixed scale11D and the liquid LQ. Also in the present embodiment, it is possible tosuppress attachment of foreign matter to the scale region 3. Thereby itis possible to suppress occurrence of a detection failure.

Fifth Embodiment

Next is a description of a fifth embodiment. In the followingdescription, components the same as or similar to those of theaforementioned embodiment are denoted by the same reference symbols, anddescriptions thereof are simplified or omitted.

FIG. 10 is a perspective view showing a part of an encoder apparatus 1Eaccording to the fifth embodiment. The encoder apparatus 1E of thepresent embodiment is a linear encoder. The encoder apparatus 1Eincludes a moving scale 4E, and a retaining member 7E that retains aliquid LQ between itself and the moving scale 4E. The moving scale 4E isa rectangular plate that travels in a straight line in the Y axisdirection. In the present embodiment, the moving scale 4E is oftransmissive type. A scale 2E (a scale region 3E) is arranged on a topsurface 4A of the moving scale 4E.

The scale region 3E is long in the Y axis direction. That is, the scaleregion 3E has a long axis (long shaft) along the Y axis direction.Furthermore, on the top surface 4A of the moving scale 4E, a firstregion 16E that is lyophobic to the liquid LQ is arranged on the +X sideof the scale region 3, and a second region 17E that is lyophobic to theliquid LQ is arranged on the −X side. The first and second regions 16E,17E are long in the Y axis direction (have a long axis along the Y axisdirection). In this manner, in the present embodiment, the area aroundthe scale region 3E is lyophobic to the liquid LQ.

The retaining member 7E retains the liquid LQ between itself and themoving scale 4E so that a local region on the surface of the movingscale 4E is in contact with the liquid LQ. The retaining member 7Eincludes a fixed scale 11E; a transmissive member 12E; and a supportmember 13E that supports the fixed scale 11E and the transmissive member12E. The fixed scale 11E is arranged at a position that faces the topsurface 4A of the moving scale 4E on which the scale region 3E isarranged. The transmissive member 12E is arranged at a position thatfaces a bottom surface 4B of the moving scale 4E. Light from a lightsource is irradiated onto the top surface 11A of the fixed scale 11E.The light being transmitted trough the fixed scale 11E is incident onthe scale region 3E of the moving scale 4E via the liquid LQ. The lightincident on the scale region 3E of the moving scale 4E is transmittedthrough the moving scale 4E, is then emitted from the bottom surface 4B,and is then incident on the transmissive member 12E via the liquid LQ.The light incident on the transmissive member 12E is transmitted throughthe transmissive member 12E, and is then incident on a detector.

Also in the present embodiment, it is possible to suppress attachment offoreign matter to the scale region 3E, and to thereby suppressoccurrence of a detection failure.

Sixth Embodiment

Next is a description of a sixth embodiment. In the followingdescription, components the same as or similar to those of theaforementioned embodiment are denoted by the same reference symbols, anddescriptions thereof are simplified or omitted.

FIG. 11 is a side cross-sectional view showing an encoder apparatus 1Faccording to the sixth embodiment. The encoder apparatus 1F is a linearencoder. The encoder apparatus 1F includes a moving scale 4F thattravels in a line it the Y axis direction, and a retaining member 7Fthat retains a liquid LQ between itself and the moving scale 4F. In thepresent embodiment, the moving scale 4F is of reflective type. Its topsurface 4A has a scale 2F (a scale region 3F). The retaining member 7Ffaces the top surface 4A of the moving scale 4F.

FIG. 12 is a perspective view of the retaining member 7F seen from the−Z side. In FIG. 11 and FIG. 12, the retaining member 7E includes afixed scale 11F, and a support member 13F that supports the fixed scale11F. The retaining member 7B has a retaining surface 6F that retains theliquid LQ between itself and the top surface 4A of the moving scale 4F.The retaining surface 6F includes a first surface 18F, and a secondsurface 19F that is closer to the top surface 4A than the first surface18F. The first surface 18F includes a bottom surface 11B of the fixedscale 11F. The second surface 19F is arranged around the first surface18F.

A light source 8 and a detector 5 are arranged at positions that facethe top surface 11A of the fixed scale 11F. In the present embodiment,the light source 8 and the detector 5 are arranged in an internal space15F of the retaining member 7F. Light is emitted from the light source 8in a state with the liquid LQ being retained between the retainingsurface 6F of the retaining member 7F and the top surface 4A of themoving scale 4F. The light emitted from the light source 8 is incidenton the scale region 3F of the moving scale 4F via the fixed scale 11Fand the liquid LQ. The light incident on the scale region 3F of themoving scale 4F is reflected of the moving scale 4F, and is thenincident on the detector 5 via the liquid LQ and the fixed scale 11F.Also in the present embodiment, it is possible to suppress attachment offoreign matter to the scale region 3F, and to thereby suppressoccurrence of a detection failure.

Note that, as shown in FIG. 13, retaining members 171 may be added tothe retaining member 7F. The retaining member 171 is, for example, astainless-steel belt, and has a retaining surface 173 that is long inthe Y axis direction in accordance with the top surface 4A of the movingscale 4F that is long in the Y axis direction. One end of each retainingmember 171 is connected to the retaining member 7F, and the other endthereof is connected to a winder mechanism 172. The size of theretaining surface 173 is adjusted by the retaining member 171 beingwound and unwound by the winder mechanism 172. In the example shown inFIG. 13, the liquid LQ is allowed to be in contact with a wide range ofthe top surface 4A, making it possible to suppress attachment offoreign, matter to the top surface 4A.

Seventh Embodiment

Next is a description of a seventh embodiment. In the followingdescription, components the same as or similar to those of theaforementioned embodiment are denoted by the same reference symbols, anddescriptions thereof are simplified or omitted.

FIG. 14 is a side cross-sectional view showing an encoder apparatus 1Gaccording to the seventh embodiment. The encoder apparatus 1G includes amoving scale 4F that travels in a line in the Y axis direction, and aretaining member 7G that retains a liquid LQ between itself and themoving scale 4F. The retaining member 70 includes a fixed scale 11G, anda support member 13G that supports the fixed scale 11G. The retainingmember 7G has a retaining surface 6G that retains a liquid LQ betweenitself and the top surface 4A of the moving scale 4F. The retainingsurface 6G includes a first surface 18G, and a second surface 19G thatis closer to the top surface 4A than the first surface 18G. The firstsurface 18G includes a bottom surface 11B of the fixed scale 11G. Thesecond surface 19G is arranged around the first surface 18G.

In the present embodiment, the encoder apparatus 1G is provided with aliquid supply port 31 that supplies the liquid LQ so as to be in contactwith the top surface 4A of the moving scale 4F including the scaleregion 3F. The liquid supply port 31 supplies the liquid LQ between themoving scale 4F and the retaining member 7G. The liquid supply port 31is arranged at a position that can face the scale region 3F. In thepresent embodiment, the liquid supply port 31 is arranged in theretaining surface 6G.

In addition, the encoder apparatus 1G is provided with a liquidcollection port 32 that collects the liquid LQ. The liquid collectionport 32 collects the liquid LQ on the moving scale 4F that faces theretaining surface 6G. The liquid collection port 32 is arranged at aposition that can face the scale region 3F. In the present embodiment,the liquid collection port 32 is arranged in the retaining surface 6G.

The liquid supply port 31 is connected to a liquid supply device 33capable of supplying the liquid LQ. The liquid supply device 33 includesa filter unit for removing foreign matter in the liquid LQ to besupplied. The liquid supply device 33 can supply a clean liquid LQ viathe filter unit. The liquid collection port 32 is connected to a liquidcollection device 34 capable of collecting the liquid LQ. The liquidcollection device 34 includes a vacuum system. Note that the liquid LQhaving been collected by the liquid collection device 34 may be returnedto the liquid supply device 33. In the present embodiment, at least apart of each of the liquid supply device 33 and the liquid collectiondevice 34 is arranged in an internal space 15G of the retaining member7G. Furthermore, in the internal space 15G, there are arranged a lightsource 8 and a detector 5. The light source 8 and the detector 5 arearranged at positions that face the top surface 11A of the fixed scale11G.

Next is a description of an example of an operation of the encoderapparatus 1G. In a state with the retaining surface 6G and the topsurface 4A facing each other, the liquid supply device 33 is activatedto supply the liquid LQ from the liquid supply port 31. The liquid LQsupplied from the liquid supply port 31 is retained between theretaining member 7G and the moving scale 4F. In the present embodiment,the liquid collection device 34 is activated concurrently with (insynchronization with; or in parallel with) the activation of the liquidsupply device 33. That is, in the present embodiment, the liquidcollection operation of the liquid collection port 32 is carried outconcurrently with (in synchronization with; or in parallel with) theliquid supply operation of the liquid supply port 31. As a result, theliquid LQ is retained between the retaining member 7G and the movingscale 4F so that the liquid LQ is in contact with a local region of thetop surface 4A of the moving scale 4F including the scale region 3F.

Light is emitted from the light source 8 in a state with the liquid LQbeing retained between the retaining surface 6G of the retaining member70 and the top surface 4A of the moving scale 4F. The light emitted fromthe light source 8 is incident on the scale region 3F of the movingscale 4F via the fixed scale 11G and the liquid LQ. The light incidenton the scale region 3F of the moving scale 4F is reflected off themoving scale 4F, and is then incident on the detector 5 via the liquidLQ and the fixed scale 11G.

In the present embodiment, the liquid LQ is supplied from the liquidsupply port 31 during the detection operation of the detector 5. Inaddition, during the detection operation of the detector 5, the liquidcollection operation of the liquid collection port 32 is carried outconcurrently with (in synchronization with; or in parallel with) theliquid supply operation of the liquid supply port 31. Also in thepresent embodiment, it is possible to suppress attachment of foreignmatter to the scale region 3F, and to thereby suppress occurrence of adetection failure.

With the liquid collection operation of the liquid collection port 32being carried out concurrently with (in synchronization with; or inparallel with) the liquid supply operation of the liquid supply port 31,it is possible to clean at least one of the top surface 4A of the movingscale 4F and the retaining surface 6G of the retaining member 7G. Forexample, even if foreign matter has attached to the top surface 4A ofthe moving scale 4F, the foreign matter is collected together with theliquid LQ by the liquid collection port 32 when the liquid collectionoperation of the liquid collection port 32 is carried out concurrentlywith (in synchronization with; or in parallel with) the liquid supplyoperation of the liquid supply port 31.

Furthermore, to clean at least one of the top surface 4A of the movingscale 4F and the retaining surface 6G of the retaining member 7G, theliquid LQ may be supplied from the liquid supply port 31, or the liquidcollection operation of the liquid collection port 32 may be carried outconcurrently with (in synchronization with; or in parallel with) theliquid supply operation of the liquid supply port 31. For example,during the halt (stop) of the detection operation by use of the detector5, the liquid collection operation of the liquid collection port 32 iscarried out concurrently with (in synchronization with; or in parallelwith) the liquid supply operation of the liquid supply port 31. Thereby,it is possible to clean (maintain) at least one of the top surface 4A ofthe moving scale 4F and the retaining surface 6G of the retaining member7G.

Note that, in the rotary-encoder-type encoder apparatuses 1, 1B, 1C, and1D as described respectively in the aforementioned first to fourthembodiments, there may be provided a liquid supply port 31, andadditionally, a liquid collection port 32.

In the aforementioned first to seventh embodiments, the descriptionshave been for the case where light transmissive water is used as theliquid LQ, by way of example. However, liquid other than water can beused so long as it has a viscosity low enough not to prevent themovement (rotation) of the moving scale. For example, as the liquid LQ,anisole (C₇H₈O), cedar oil, glycerin, or the like can be used.

In the aforementioned embodiments, the descriptions have been for thecase where the liquid LQ is retained between the moving scale and theretaining member, by way of example. However, the liquid LQ may beretained between the moving scale and the detector. In that case, forexample if the fixed scale is omitted and, instead, a scale (a grating)is arranged on the light-receiving surface of the detector, then it ispossible to detect the position information on the moving scale.

Eighth Embodiment

Next is a description of an eighth embodiment. In the followingdescription, components the same as or similar to those of theaforementioned embodiment are denoted by the same reference symbols, anddescriptions thereof are simplified or omitted.

FIG. 15 is a side cross-sectional view showing an example of an encoderapparatus 1H according to an eighth embodiment. In the aforementionedfirst to seventh embodiments, the descriptions have been for the casewhere the encoder apparatus is an optical encoder that optically detectsthe scale, by way of example. Characteristic features of the eighthembodiment will be described for the case where the encoder apparatus 1His an electrostatic encoder as disclosed in, for example, JapaneseUnexamined Patent Application, First Publication No. 2004-257974, by wayof example.

In FIG. 15, the encoder apparatus 1H includes a rotor 4H on which acoupling electrode 2H is arranged, and a stator 7H capable of retaininga liquid LC between itself and the rotor 4H. Within the XY plane, thestator 7H has a ring shape. The stator 7H includes atransmitting-receiving electrode 5H. The transmitting-receivingelectrode 5H detects electrostatic force of the rotor 4H. Thetransmitting-receiving electrode 5H is capable of being in contact withthe liquid LC, and retaining the liquid LC between itself and the rotor4H. The liquid LC is insulating. The liquid LC is retained between therotor 4H and the stator 7H. Also in the present embodiment, attachmentof foreign matter to the rotor 4H or the stator 7H is suppressed.Thereby, it is possible to suppress occurrence of a detection failure.

In the eighth embodiment, a liquid supply port that supplies the liquidLC may be provided. In addition, a liquid collection port that collectsthe liquid LC may be provided.

Ninth Embodiment

Next is a description of a ninth embodiment. In the followingdescription, components the same as or similar to those of theaforementioned embodiment axe denoted by the same reference symbols, anddescriptions thereof are simplified or omitted.

FIG. 16 is a side cross-sectional view showing one example of an encoderapparatus 1J according to the ninth embodiment. Characteristic featuresof the eighth embodiment will be described for the case where theencoder apparatus 1J is a magnetic encoder as disclosed in, for example,Japanese Unexamined Patent Application, First Publication No.2008-039673, by way of example.

In FIG. 16, the encoder apparatus 1J includes a rotor 4J with apermanent magnet, and a retaining member 7J capable of retaining aliquid LD between itself and the rotor 4J. The retaining member 7J has aring shape, and is arranged so as to surround the rotor 4J. Theretaining member 7H has a magnetic field detection element 5J. Themagnetic field detection element 5J detects a magnetic field of therotor 4J. The magnetic field detection element 5J is capable of being incontact with the liquid LD and retaining the liquid LD between itselfand the rotor 4J. The liquid LD is a magnetic liquid. Note that theliquid LD may be a non-magnetic liquid. The liquid LD is retainedbetween the rotor 4J and the retaining member 7J. Also in the presentembodiment, attachment of foreign matter to the rotor 4J or theretaining member 7J (the magnetic field detection element 5J) issuppressed. Thereby, it is possible to suppress occurrence of adetection failure.

In the eighth embodiment, a liquid supply port that supplies the liquidLD may be provided. In addition, a liquid collection port that collectsthe liquid LD may be provided.

The required elements of the aforementioned first to ninth embodimentsmay be appropriately combined. Furthermore the disclosures in all of thePatent Publications related to encoder apparatuses and the like cited inthe above respective embodiments and modified examples are incorporatedherein by reference.

1. An encoder apparatus comprising: a first scale member with a scaleregion including a scale and a lyophobic region having a lyophobicproperty, the lyophobic region arranged on an external side of the scaleregion; a detector that detects light from the scale region; and aretaining member with a retaining surface that faces the scale regionvia a gap and retains a liquid between the retaining surface and thescale region.
 2. The encoder apparatus according to claim 1, wherein theretaining member retains the liquid so that the liquid is locally incontact with the first scale member.
 3. The encoder apparatus accordingto claim 2, wherein the first scale member comprises a plate memberhaving a first surface and a second surface, in which the first surfaceand the second surface face in opposite direction; and the retainingsurface of the retaining member faces a part of the first surface. 4.The encoder apparatus according to claim 2, wherein the first scalemember is a plate member having a first surface, a second surface, and aside surface that connects the first surface with the second surface, inwhich the first surface and the second surface face in oppositedirections; and the retaining member comprises a first portion thatfaces at least a part of the first surface; a second portion that facesat least a part of the second surface; and a third portion that connectsthe first portion with the second portion, and faces the side surface.5. The encoder apparatus according to claim 3, wherein the first scalemember comprises a rotatory circular plate; and the retaining surface ofthe retaining member comprises a ring shape in accordance with thecircular plate.
 6. The encoder apparatus according to claim 3, whereinthe first scale member comprises a rectangular plate; and the retainingsurface of the retaining member comprises a rectangular shape inaccordance with the rectangular plate.
 7. The encoder apparatusaccording to claim 1, wherein the scale region is lyophilic to theliquid.
 8. The encoder apparatus according to a claim 1, wherein asurrounding region of the scale region is the lyophobic region.
 9. Theencoder apparatus according to claim 1, wherein the retaining surfacecomprises a first surface that faces the first scale member via a firstgap; and a second surface that faces the scale member via a second gapthat is smaller than the first gap.
 10. The encoder apparatus accordingto claim 9, wherein at least a part of the second surface faces anexternal region of the scale region; and the external region islyophobic to the liquid.
 11. The encoder apparatus according to claim 9,wherein at least a part of the first surface faces the scale region, andthe first surface is lyophilic to the liquid.
 12. The encoder apparatusaccording to claim 9, wherein the second surface is arranged on at leasta part around the first surface.
 13. The encoder apparatus according toclaim 9, wherein the second surface is arranged on at least a part of acircumferential edge of the retaining surface.
 14. The encoder apparatusaccording to claim 13, wherein the second surface is inclined so as tobe gradually closer to the first scale member in a direction from acenter of the retaining surface to an external side thereof.
 15. Theencoder apparatus according to claim 1, wherein the first scale membercomprises a protrusion portion at a position that faces a vicinity of acircumferential edge of the retaining surface, in which the protrusionportion protrudes toward the retaining surface.
 16. The encoderapparatus according to claim 15, wherein the protrusion portioncomprises an inclined surface that is inclined so as to be graduallycloser to the retaining surface in a direction from a center of theretaining surface to an external side thereof.
 17. The encoder apparatusaccording to claim 1, wherein the retaining member comprises atransmissive portion through which at least a part of the light can betransmitted, and the detector detects the light from the first scalemember via the transmissive portion.
 18. The encoder apparatus accordingto claim 1, wherein the retaining member comprises a second scale memberthat is different from the first scale member.
 19. The encoder apparatusaccording to claim 18, wherein the second scale member is arrangedbetween the detector and the first scale member.
 20. The encoderapparatus according to claim 1, wherein the retaining member comprisesthe detector.
 21. The encoder apparatus according to claim 1, furthercomprising a liquid supply port that supplies the liquid between thefirst scale member and the retaining member.
 22. The encoder apparatusaccording to claim 21, wherein the liquid supply port is arranged at theretaining surface.
 23. The encoder apparatus according to claim 1,further comprising a liquid collection port that collects the liquid.24. The encoder apparatus according to claim 23, wherein the liquidcollection port is arranged at the retaining surface.
 25. The encoderapparatus according to claim 1, wherein the detector detects the lightvia the liquid.
 26. The encoder apparatus according to claim 1, whereinthe first scale member has a first surface including the scale regionand a second surface; the retaining surface faces a part of the firstsurface and a part of the second surface; and the lyophobic region isarranged on the part of the first surface and the part of the secondsurface.
 27. An encoder apparatus comprising: a first scale member witha scale region including a scale and a lyophobic region having alyophobic property, the lyophobic region arranged on an external side ofthe scale region; a detector that detects the scale of the scale region;and a liquid supply port that supplies a liquid so as to be in contactwith the scale region.
 28. The encoder apparatus according to claim 27,wherein the detector detects the scale via the liquid.
 29. The encoderapparatus according to claim 27, wherein the liquid is supplied during adetection operation of the detector.
 30. The encoder apparatus accordingto claim 27, wherein the liquid is supplied in order to clean the firstscale member.
 31. The encoder apparatus according to claim 27, whereinthe liquid supply port is arranged at a position that can face the scaleregion.
 32. The encoder apparatus according to claim 27, furthercomprising a liquid collection port that collects the liquid.
 33. Theencoder apparatus according to claim 32, wherein the liquid collectionport is arranged at a position that can face the scale region.
 34. Theencoder apparatus according to claim 32, wherein a liquid collectionoperation of the liquid collection port is carried out concurrently withat least a part of a liquid supply operation of the liquid supply port.35. The encoder apparatus according claim 27, wherein the scale membercomprises a magnetic member; and the detector detects a magnetic forceof the scale member.
 36. The encoder apparatus according to claim 27,wherein the scale member includes an electrode member; and the detectordetects an electrostatic force of the scale member.